In general, the so-called heat dissipation is eventuality always to dissipate heat to air. However, whether convection or thermal radiation is related to the surface area of a heat dissipating surface of an object. Now, with the increase of a power of a heat generating element, in order to increase the surface area of the heat dissipating surface of a heat sink, the heat sink is becoming bigger and more bulky, but the efficiency is relatively low. In particular, a distance from the heat generating element to the heat dissipating surface is greatly increased while the heat dissipating surface is increased, such that the temperature difference required for heat transfer over this distance is also greatly increased. This makes heat dissipation of some elements such as a high-power LED chip reach at a dead end and currently become a key obstacle to rapid development of LED lighting.
As another aspect of heat exchange, heat absorption is exactly the same.